
- 189%.) | Eméryology. 917 
EMBRYOLOGY.! 
Studies in Cephalopods.?—Dr. S. Watase, of Clark University, 
publishes under the above title No. 1 of his contributions on the cleavage 
of the ovum. The opening paragraph indicates the contents of the paper. 
‘* In the following pages I will first attempt to treat the general mor- 
phology of the animal ovum from the standpoint of some embryological 
and morphological facts and theories. In the next place, the relation 
of the external phenomena of cleavage, as shown in the behavior of the 
cytoplasm, to the internal phenomena of nuclear or karyokinesis will 
be discussed. In this connection some theories on karyokinesis will 
examined, my interpretation of the cleavage phenomena being that 
they are essentially the analysis of the potential tissues contained in 
the cleavage nucleus, and this karyokinesis is the method of such 
analysis and the achromatic spindle the instrument used in the analy- 
sis. The cleavage of the squid will then be described, and finally . 
variations in the cleavage of the same animal will be discussed.’’ It 
is impossible to here go into the theoretical discussions that occupy the 
larger part of the paper, but the following quotations, taken here and 
there, may serve to give some idea of the author’s convictions. From 
a'review of the literature the author concludes that ‘‘ however diverse 
the examples, they all point to one and the same conclusion,—namely, 
that in the metazoan ovum and its derivations the tissue cells are more 
than a homogeneous, isotropic mass of protoplasm devoid of a definite 
symmetry. The study of the karyokinetic figure shows, Van Beneden 
points out, that the cell is not only unaxial, but also bilateral. In 
several forms of ova, carefully studied, the axes of the karyokinetic 
figure correspond in a definite way with the recognizable axes of a 
given ovum, the external shape of which is chiefly determined by the 
quantity and distribution of the food yolk. The axes thus determined 
are maintained through the different stages of growth, and give rise to 
definite axes of the larve or of the adult organism. If these facts 
be more firmly established by the further investigation of the subject, 
we may say with Van Beneden ‘that the old theory of evolution is not 
deprived of all foundation, as is generally believed to-day.’ 
In this connection a communication from Dr. C. Ishikawa is of 
great interest,—viz., that the summer and winter eggs of a “certain 
1 Edited by Dr. T. H. Morgan, Johns Hopkins University, Baltimore, Md. 
2 Journal Morphology, Vol. IV., No. 3. 


